Dispensing pumps for delivering measured quantities of a liquid are well known. Such pumps have long been used for a myriad of applications as an effective and efficient means of delivering liquids such as perfumes, medicines, air fresheners, and many other liquids. However, although the prior art is highly developed, certain deficiencies in this general area exist.
U.S. Pat. No. 4,082,222 to Boris, U.S. Pat. No. 4,941,595 to Montaner et al. and U.S. Pat. No. 5,156,304 to Battegazzore disclose spray pumps for delivering liquids. Each of the prior art pumps has a hollow body with a piston slidably disposed therein. The body and piston define a chamber containing the liquid to be dispensed. A rod fits slidably inside the piston and is forced into contact therewith by a spring. During use, force is applied to the rod causing it to move downward. When a certain pressure is reached in the chamber, the spring is compressed to open a channel between the rod and the piston so that the liquid can flow therethrough and be dispensed. A disadvantage of these prior art designs is that the pressure required to open the channel so that the liquid may be dispensed is a function of only the force applied by the operator and the spring forces. As such, the pumps do not have a smooth feel during pumping by the operator. Moreover, delivery of the liquid may not occur in a uniform fine mist because when the pump is actuated slowly, small amounts may leak out with a pressure insufficient to create such a mist. Another disadvantage of these prior art designs is that a high actuation force is required to dispense the liquid.
U.S. Pat. No. 4,960,230 to Marelli and U.S. Pat. No. 5,482,188 to Lina disclose fluid dispensing pumps similar to those discussed above. A disadvantage of these prior art designs is that the piston is caused to move upwards during pump actuation. This upward movement of the piston is not consistent with a pump having a smooth feel during actuation. A further disadvantage of the device disclosed in the Marelli patent is that no mechanical releasing mechanism is provided to keep the fluid delivery channel fully sealed until the desired critical pressure is reached. This deficiency may lead to small amounts of the liquid to be dispensed leaking out of the actuator prematurely with a pressure insufficient to create the desired fine uniform mist.
What is desired, therefore, is a non-throttling dispensing pump for delivering measured quantities of a liquid which delivers the liquid in a uniform fine mist, which is low in profile, which has a low force to actuate, and which has a smooth feel during actuation.